Air Circuit Breaker (ACB)

Introduction                         
              Air circuit breaker (ACB) is an electrical device used to provide over current and short circuit protection for electrical circuits over 800 Amps to 10k Amps.These are usually used in low voltage applications below 450v.

Types of Air Circuit Breakers 
             There are mainly two types of Air circuit breakers are available .
  1. Plain air circuit breaker or cross blast circuit breaker.
  2. Air blast circuit breaker.
           Air blast circuit breaker is further sub divided .
  • Axial blast breaker
  • Axial blast with sliding contactor
Major Components of ACB
               The major components of Air circuit breaker are poles, The arc chuts, The base frame the operating mechanism.
Poles
                 The Poles include.
  • The fixed and moving Arcing contacts.
  • The fixed and moving main contacts.
  • Epoxy resin bushings.
  • Moving isolating contacts ( Main disconnects).
  • Pneumatic blow nozzles.
  • The connections to the coils are chute.
Arc Chutes
              The Arc Chutes contains.
  • The blowout coils.
  • The are runners.
  • Supporting insulating plates.
  • The arc runners.
  • Supporting insulating plates.
  • The magnet pole pieces.
Working Principle
                  When the fault occurs the main contacts are separate first, and the current is shifted to the arcing contacts. Now the arcing contacts are separate and the arc is drawn between them .This arc is forced upwards by the electromagnetic forces and thermal action,The arc ends travels along the arc runner,The arc moves upward and is split by the arc splitter plates.

 Application and uses of ACB
  • It is used for protection of plants,electric machines,transformers,capacitors and generators.
  • Air circuit breaker is also used in the electricity sharing system and GND about 15kv.
  • Also used in low as well as high currents and voltage applications.
Drawback of ACB
                 A drawback of arc chute principle is its inefficiency at low currents where the electromagnetic fields are weak.The chute itself is not necessarily less efficient in its lengthening and deionizing action than at high current, but the arc movement into the chute tends to become slowers and high speed interruption is not necessarily obtained.
                

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